Tractor beam

A tractor beam or stabilizing beam was an attenuated linear graviton beam used by starships and space stations to control the movement of external objects. The tractor beam placed spatial stresses on the object in specific areas, allowing it to hold the "tractored" object in a fixed location or alter its position and/or trajectory. While tractor beams were normally used to pull objects towards the beam source – usually to tow objects – conversely, they could also be set to repel objects. They were most often employed to tow a disabled or vulnerable ship to safety, or sometimes, used by an enemy ship to control the movement of the target vessel. (TOS: "Who Mourns for Adonais?"; TNG: "The Naked Now", "The Battle", "The Masterpiece Society", "Cause and Effect"; DS9: "Emissary"; VOY: "Scorpion", "Renaissance Man")

Tractor beams were generally only used at sub-warp velocities. To safely tow a vessel at warp speed, the target vessel's engines had to be deactivated to avoid shearing forces against towing vessel. A tractor beam could be used at warp speed only if both vessels' speeds were exactly matched. (VOY: "Day of Honor", "Renaissance Man"; TNG: "Final Mission", "The Emissary")

The 2006 video game Star Trek: Legacy established that the tractor beams had started being used by Starfleet during the Earth-Romulan War around the year 2159, when Enterprise had its grapplers replaced with the more advanced technology.

If a vessel's tractor beam is strong enough, its graviton field can reinforce the structural integrity of a target vessel, keeping its hull from succumbing to stresses normally exhibited by a tractor field. (DS9: "Captive Pursuit")

Tractor beam as used for towing

When using a tractor beam to force another vessel out of warp speed, otherwise known as a "warp tow", both vessels needed to match velocity at the time of the tractor beam initiation. This brought tremendous risk to both vessels. However, if both vessels' hulls were strong enough to withstand the stress, they could both be brought out of warp with the tractor beam still engaged if the towing vessel carefully disengaged the warp drive while engaging the impulse engines. (DS9: "Paradise")

An internal tractor beam emitter in the shuttlebay of the USS Enterprise-D

The Borg favored the use of a considerably more advanced tractor beam when engaging in combat. The Borg beam was capable of rapidly draining a vessel's shields while holding the vessel in place, rendering it virtually helpless against the cutting beam that it was often used in conjunction with. Furthermore, the sheer size of the Borg cube permitted the tractor beam to be used with considerable effectiveness against even ships as large as the USS Enterprise-D. They also had the ability to utilize tractor beams at warp velocities. (TNG: "Q Who"; DS9: "Emissary"; VOY: "Scorpion")

In 2371, B'Elanna Torres devised a plan to create a subspace tractor beam, which was a standard tractor beam modified to match subspace interference. This modification required more power than a standard tractor beam and could cut through subspace interference. This tractor beam was also able to project long distances. (VOY: "Parallax")